During dental procedures, it is often difficult for the patient to hold his mouth open for extended lengths of time due to muscle fatigue. Mouth props, or bite blocks, are often lodged between a patient's upper and lower teeth to hold the mouth open. However, a desirable mouth prop must also be comfortable for the patient and usable with different patients, or with a single patient under varied conditions.
Further, to enable the dentist to maintain the patient's mouth open to a degree most comfortable for the patient and to provide maximum access to the inside of the patient's mouth, a mouth prop ought to be adjustable.
Several adjustable mouth props have been designed. In U.S. Pat. No. 2,023,288 and RE No. 20,389 to Pickett, a mouth prop made adjustable by a wedge having beveled notches was disclosed. The wedge is forced between opposed jaw engaging members to open the patient's mouth. The beveled notches engage a lug on one of the jaw engaging members to secure the wedge in place. However, the use of notches and a lug in the Pickett mouth prop provides for only incremental adjustment. Also, the beveled notches of the Pickett mouth prop provide for smooth adjustment only when the wedge is inserted further into the mouth. This means that, were the patient's mouth to be closed only slightly, the wedge has to be completely retracted. The fact that the patient first has to open his mouth in order for the wedge to be removed and repositioned means that the dental procedure has to be interrupted, thereby prolonging patient discomfort.
Further, the Pickett mouth prop comprises two pieces. This poses the risk that one of the pieces may be lost by the dentist or swallowed by the patient. Furthermore, the wedge and the jaw engaging members form a barrier on one side of the patient's mouth which obstructs the view of the working area of the mouth for an assistant, were assistance required during the dental procedure.
U.S. Pat. No. 2,103,115 to Mizzy, et al. discloses a dental jack that provides for continuous adjustment by means of a screw and a threaded sleeve. Although the Mizzy mouth prop allegedly provides an unobstructed view of the working area of the patient's mouth, it is unstable when used solely as a mouth prop, due to its pin-shaped contact with the teeth.
U.S. Pat. Nos. 856,352 to Magoon and 2,019,060 to Thibert both teach mouth props having a spring surrounding a telescopic shaft connecting two jaw engaging members to hold open a patient's mouth. The telescopic shaft of both Magoon and Thibert mouth props have an outer and an inner shaft member. In order to adjust the Magoon mouth prop, the outer shaft member is tilted to rest on the notches of the inner shaft member. The Thibert mouth prop relies on friction between the tilted outer shaft member and the inner shaft member to adjust and maintain the occlusal opening. These mouth props are designed to be used with a patient who is under anesthesia--when the jaw muscles of the patient are relaxed and do not need strong support. Therefore, these mouth props are not sturdy enough to support fatigued and possibly tense muscles of a conscious patient.